The HQ is a type of non-locking, two-pivot synchronized tremolo bridge sourced on Ibanez guitars.
The HQ is a non-floating tremolo in the style of a Fender Strat or traditional Wilkinson tremolo. It has a stainless steel plate and saddles and hardened steel knife-edge pivots. It has a low profile to minimize interference with the players hands and a push-in tremolo arm for easy removal. It takes a non-threaded 5mm diameter tremolo arm.
The HQ tremolo is generally used in conjunction with locking tuning machines to enhance tuning stability when the tremolo is used.
A simpler version of the HQ tremolo was introduced a few years later as the HQ-J tremolo, or HQ Jr.